Subsurface pump



Nov. 5, 1963 C, L, ENGLISH 3,109,379

v SUBSURFACE PUMP 6 Sheets-Sheet 2 Nov. 5, 1963 c. l.. ENGLISH sUBsURFAcE PUMP Filed Feb. 1s. 1961 Nov. 5, 1963 C. L. ENGLISH SUBSURFACE PUMP Filed Feb, l5, 1961 soo 524 6 Sheets-Sheet 3 40d M 40e 'M 40a 4 Q0 F i r3.- E

INVENTOR.

Nov. 5, 1963 Filed Feb. l5. 1961 C. L. ENGLISH SUBSURFACE PUMP 6 Sheets-Sheet 4 INVEN TOR. CHAQLf-s n /vcyL/sH @fw/W Nov. 5, 1963 c. l.. ENGLISH 3,109,379

sUBsuRFAcE PUMP Filed Feb. 15, 1961 e sheets-sheet e 62a am 8/4 520 as? 83e 22 sa J a/a a 42 IN VEN TOR.

United States Patent O 3,109,379 SUBSURFACE PUMP Charles L. English, 2204 E. 25th Place, Tulsa, Dida. Filed Feb. 13, 1961, Ser. No. 89,053 4 Claims. (Cl. 1013-46) This invention relates generally to improvements in subsurface pumps utilized in oil wells land the like, and more particularly, but not by way of limitation, to fluid operated `subsurface pumps and fluid motors therefor.

Subsurface fluid operated pumps have lbeen known in the oil producing industry for many years. A complete pump unit comprises a fluid motor and a reciprocating type pump connected in tandem relation rand being of a size to be raised and lowered through a well bore. In the operation of such pump units, the power fluid (which is normally clean oil) is pumped under relatively high pressure downwardly to the fluid motor of the pump unit which provides a reciprocation of the motor and the pump. The pump draws in the well fluids and pumps the well fluids upwardly to the top of the |well, usually along with power fluid exhausting from the motor or engine end of the unit. It may also be noted that such pump units may be either an Linsert type or a free type. An insert type of pump unit is suspended `on the lower end on a string of relatively small diameter tubing through which power fluid is fed Idownwardly to the fluid motor. The pumped well fluids and exhausting power fluid are directed upwardly through a larger string of tubing or through the well casing in which the pump unit is seated. A free type pump unit is provided with suitable cups and is of a size such that the pump unit can be literally pumped upwardly and downwardly through one string of tubing into a pump cavity communicating with the tubing in which the pump is ldisposed and with a separate string of tubing. In operation of the free type of pump, the two strings yof tubing are normally arranged side-by-side and power oil is forced down one of the tubings while the pumped well `fluids and exhausting power fluid are directed upwardly through the other tubing.

Until recently, subsurface hydraulic or fluid operated pump units have been considered economically feasible in wells ranging from 4five thousand to ten thousand feet having what may be considered 1a rather moderate production, such as one hundred to two hundred barrels per day. Very few wells were drilled deeper than ten thousand feet and the production in relatively shallow wells in this country is usually relatively small, such as less than one hundred barrels per day. Most shallow wells having limited production can normally be pumped more efficiently by means of a sucker rod type pump having a surface power unit. However, with the advent of deeper wells and with the advent of water flooding and similar operations, the potential for subsurface hydraulic pumps has tbeen substantially increased. Subsurface hydraulic pumps may be used in these latter two conditions providing certain problems `are solved in the construction of the pump units.

It is rather apparent that, assuming a given production, the deeper the well, the more horse power required for lifting the well fluids and exhausting power fluid to the top of the well. Furthermore, 4it rather apparent that the diametrical dimensions of a hydraulic pump uni-t are limited by the diameter of the well in which the pump is to be used. One method :of increasing the horse power output of the engine `end of a pump unit is to utilize a conventional fluid motor and merely increase the pressure of the power oil being fed to the motor. In theory, this solution appears to be very efficient, since the minimum frictional losses arise though pumping a limited 3,109,379 Patented Nov. 5, 1963 amount of oil at a high pressure. However, the pressure require at the well head for this type of method, such as 10,000 p.s.i. and even up to 20,000 p.s.i., becomes extremely dangerous. Special fittings and piping are required to handle the high pressure fluid, and a leak could easily kill workmen around the well head.

The use of water flooding and similar secondary recovery Ioperations materially increases the pro-duction in the producing wells being used. These flooding operations may be used in formations of substantially Iany depth, but are presently being used Vmostly in relatively shallow formations. In any event, how-ever, a subsur- `face hydraulic pump must have substantial capacity in order to provide the require production. Here again, it will be noted that the diametrical size of a pump unit is limited by the diameter of the well bore in which it is used. A` double acting pump unit normally has a greater capacity than a single acting pump unit for a given diameter of pump cylinder. However, a double acting pump requires the use of two complete sets of valving and, in the diametrical limitations of most pump units, the valves must be extremely small which increases the cost of the pump unit and usually 'decreases the efliciency of the pump unit. Also, of course, the stroke length of a pump unit may be increased to increase the capacity, but this involves difficult alignment problems which will increase the cost of the pump unit. In addition to the foregoing, it should be noted that the horse power of a pump unit must be increased when the capacity of the pump unit is increased, and this is particularly apparent in the deeper wells.

The present invention contemplates a novel fluid and pump, as well as a novel combination fluid motor and pump. The novel fluid motor of this invention contemplates the use of a piston assembly having oppositely facing sets of working areas against which power fluid is applied for reciprocation of the piston assembly and wherein at least one set of the working areas has a total cross-sectional area larger than the cross sectional area of the interior of the cylinder in which the piston assembly reciprocates. The increased working faces of the piston assembly provide an increased horse power output for the motor without the necessity of increasing the pressure of the power fluid. The quantity of power fluid required is increased, but this requirement is more than offset by being able to minimize the pressure requirements for the power fluid. The valve mechanism for the engine piston assembly may be located either in the piston assembly or in one head of the engine cylinder. In either event, a passageway is provided through the piston assembly from the valve chamber to supply and exhaust power fluid from one set of the working faces of the piston assembly to minimize the overall diameter of the motor and provide the most economic utilization of space. This construction of a fluid motor or engine is sometimes herein referred to as a complex engine end to distinguish it from a conventional fluid motor having working areas on the piston no larger than the crosssectional area of the motor cylinder.

The novel pump of the present invention contemplates a single acting pumping assembly having a plurality of communicating pump chambers into which well fluid is drawn on one stroke of the pump and from which the well fluids are discharged on the opposite stroke of the pump. This construction requires a single well fluid inlet and a single standing valve assembly to minimize the cost of construction and minimize the resistance to the flow of well fluids being drawn into the pump. This construction also requires only a single traveling valve assembly with similar economies and efficiencies. When operating conditions demand, an auxiliary traveling valve assembly may be provided to discharge a minor portion of the pumped well fluids from one of the pump chambers into the production column in order that the hydrostatic head of the production column will be imposed upon an additional upwardly facing area of the pump piston assembly to facilitate the downstroke of the pump. The plural communicating pump chambers provide a pumping capacity as-large as a double acting pump without the shortcomings of a double acting pump. This construction of a reciprocating pump is sometimes herein referred to asa complex pump end to distinguish it from a simple, conventional single acting pump end 'of a pump unit.

The novel pump unit of this invention, which comprises the combination of a fluid motor and pump, contemplates a subsurface hydraulic pump unit capable of operating in wells of substantially any capacity and depth.V In relatively shallow Wells having substantial production, the novel pump having a plurality of communicating pump chambers is combined with a rather conventional engine or motor end to accommodate the increased production without increasing the pressure or quantity requirements for the power iluid any appreciable degree. In deeper wells having normal production but relatively highhorsepower requirements for lifting the production iluids, a conventional single acting pump is combined with a fluid motor having increased area working faces to provide the increased horsepower without increasing the pressure requirements of the power fluid to any appreciable extent.` In wells having substantial production along with substantial horsepower requirements, the novel pump having plural communicating pump chambers is combined with a iluid motor having increased area Working faces. In all of the fluid motor and pump combinations, it is preferred to utilize a hollow connecting rod between the engine piston assembly and the pump piston assembly wln'ch forms an exhaust passageway for power fluids from the engine or motor, such that the exhausting power iiuid is combined with the pumped well fluids in the pump end of the unit and will provide a cleaning action for the pump piston assembly to minimize wear of the pump piston assembly. i

An important object of this invention is to provide a subsurface fluid operated pump unit which will efficiently and economically produce an oil well having substantially Vany production and horse power requirements.

Another object of this invention is to provide a subsurface iiuid operated pump unit which is particularly adapted for producing wells being stimulated by water Y flooding or the like.

Another object of this invention is to provide a reciprocating pump having the efficiencies and economies of a single acting pump, but having the capacity of a double acting pump.

A further object of this invention is to provide a reciprocating type pump having limited diametrical requirements and yet providing the maximum in capacity with the minimum of valving.

Another object of this invention is to provide a novel fluid motor particularly adapted for a subsurface pump unit which will provide the maximum in horse power *output with the minimum pressure requirements for In the drawings:

FIGURE 1 is a vertical sectional view through the -uid motor or engine end of a pump unit.

FIGURE 2 is a vertical sectional view through the complex pump end `of a pump unit .and is a continuation from the lower end of FIG. l.

FIGURE 3 is a schema-tic vertical sectional View of the pump unit structurally illustrated in FIGS. l and 2 which is provided to more clearly illustrate the novel features of the pump unit and its operation.

FIGURE 4 is a schematic vertical sectional view of a modiied pump unit having the same general combination as the pump unit illustrated in FIGS. 1, 2 and 3.

FIGURE 5 is a vertical sectional view through the upper portion of a pump unit utilizing a complex engine end.

FIGURE 5A is a horizontal cross-sectional view through the pump unit illustrated in FIG. 5 as taken along ylines 5A-5A of FIG. 5.

FIGURE 6 is a vertical sectional view of the lower portion of a pump unit and is a continuation from the lower end of FIGVS.

FIGURE 7 is a schematic vertical sectional view through a pump'unit of the type'illustrated structurally in FIGS. 5, 5A and 6.;

FIGURES 8 and 9 are schematic vvertical sectional views through pump units having the same general combination of a complex engine yand simple pump Vend as illustrated in FIGS. 5 through 7.

FIGURES `10, 1 1 and 12 comprise a vertical sectional View through a pump unit having both a complex engine end and complex pump end, with FIG. l0 being the upper portion of a pump unit, FIG. 11 being the central portion of the pump unit and FIG. 12 being the lower end of the pump unit.

FIGURE 13 is a schematic vertical sectional view through :a pump unit of the type illustrated structurally in FIGS. 10, 11 and 12.

FIGURE 14 is a schematic verticalV sectional view -through another type of pump unit having a complex Referring to the drawings in detail, and particularly FIGS. l and 2, reference character 26 generally designates a complete fluid operated pump unit generally comprising what may be considered a simple or conventional engine end 22 and a complex pump end 24 connected in tandem relation. The engine end 22` comprises an engine cylinderv 26 Iof the desired diametrical and lengthwise dimensions and having an elongated upper cylinder head 2-8.

The engine piston 30 is sli'dingly sealed in the engine cylinder 26 by suitable piston rings 32 for reciproc-ation in the engine cylinder in response to the application of fluid pressures against the upper and lower faces of the piston as will be hereinafter set forth. The engine piston 30 is tubular in conliguration to provide a bore 34 extending lengthwise -therethrough A plurality of ports 36 extend at an angle 'through a portion of the engine piston 30 and provide communication betweenthe bore 34 and the lower face of the engine piston for directing power tluid to and. from the lower end portion of the engine cylinder 26, as `will be described. The lower end of the bore 34 is threaded for connection with the upper end of a connecting rod 38 which extends downwardly from the engine piston 30 into connection with the pump end 24, as will also be described. The upper end of the bore 34 is also threaded to receive the lower threaded end of a tube 40 extending upwardly from the engine piston 30' concentrically with respect to the engine cylinder 26. The tube 40 cooperates -with the bore 34 and polts 36 to convey power fluid toand `from the lower face of the engine piston 30l and operates to aotuate the valve mechanism of the engine 22, as will be described.

The upper cylinder head 23 is secured to the upper end of the engine cylinder 26 by means of a tubular adapter 42 having an inner bore 44 of a size to loosely receive the upper end portion of the tube 40 and having =a plurality of vertically extending bores y46 therethrough spaced circumferentially around the central bore d4 in communication, at their upper ends, with an annular chamber 43 formed in the lower end portion of the cylinder head 28 to conduct power fluid to and from the upper end of the engine cylinder 26, as will be described. A packer body 50 is secured to the lower end of the adapter 42 by means of a sleeve 52, such lthat the packer body v50 is spaced downwardly from the 'adapter 42 and encircles the tube 40 in all operating positions of the engine piston 30. Suitable packing 54 is secured in the packer body 50 in sealing relation around the tube 40 by means of la retainer ring 56 threaded into the lower end of the packer body to prevent the leakage of iluid between the upper end of the engine cylinder 26 and the inner bore 44 ofthe adapter 42.

The valve mechanism for the engine end 22 comprises ia sleeve type main valve `5S and a pilot valve 60 for controlling the operation of the main valve. The pilot valve 60 is a piston type valve and is reciprocally `disposed in a valve chamber 62 formed in the lower end portion of the cylinder head 2S in axial alignment with the engine cylinder 26. A cylindrical valve extension 66 on the lower end of the pilot valve l60 reciprocates in a reduced diameter portion of the bore 44 in the adapter 42 for connection with a trip rod `6? extending downwardly into the tube '40 carried by the engine piston 30. The trip rod 63 extends loosely through an annular nut 70 secured in the upper end of the tube 40 and is provided with an enlarged head portion 72 on the lower end thereof for contact by the nut 70 at the lower end of the downstroke of the engine piston 36' for shifting the pilot valve 60, as will be described. It will also be noted that a nut 74 is secured on the trip rod 68 against the lower end of the pilot valve extension `66 for contact by the nut 70 near the end of the upstroke of the engine piston 30.

A circumferential groove 76 is formed around the medit al portion of the pilot valve 60 in communication with a slanting bore 78 extending downwardly through the pilot valve `60 to the upper end of the pilot valve extension 66 to control the ilow of huid between a pair of bores 80 and 82 extending radially through the upper cylinder head 26 from the pilot valve chamber `62. The bore 30- communicates with the exterior of the cylinder head 25 and the bore `82 communicates with a vertical bore 34 which communicates with the main valve 53 as will be described. Also, another vertical bore 86 extends through the head 28 from the lower end of the main valve charnber to a groove 87 formed in the medial portion of the pilot valve chamber 62 to control the movement of the main valve 5S. i

The main valve 53 is reciprocally disposed in a valve chamber 88 formed in the upper end portion of the engine cylinder head 28 in axial alignment with the pilot valve chamber 62 to control the ilow of power fluid to and from passageways 9-0and 92 communicating with the opposite end faces of the engine piston 30. The passageway 90 comprises a bore extending substantially vertically through the cylinder head 28, ports 94 in the upper end of the adapter 42, the inner bore 44 of the adapter 42, ports 96 in the upper end portion of the tube 4t) below the nut 70, the bore of the tube 40, the bore 34 of the engine piston 30 and the bores 36 in the engine piston 30. It will also be noted that the passageway 90 communicates with lthe upper end of the pilot valve chamber 62 through a horizontal bore 98 to assist in the operation of the pilot valve 60, as will be described. The upper end of the passageway 90 communicates with the upper central portion of the valve chamber 88 through ports 100` and 102 formed in an insert 104 rigidly held in the valve chamber 8S around the upper end portion of the main valve 58 by an adapter 106. The adapter 106 is in turn connected to a string of tubing (not shown) extending from the top of the well in which the pump unit 20 is disposed and is provided with a bore 10.8 therethrough forming an inlet for power fluid into the upper end of the valve chamber 88.

The passageway 92 comprises a bore extending upwardly through the cylinder head 2S from the annular chamber 48 and the vertical bores 46 in the adapter 42 to communicate with the upper end of the engine cylinder 26 and the upper face of the engine piston 30. The upper end of the passageway 92 communicates with an intermediate portion of the valve chamber 38 below the insert 1014 through one or more ports 110.

As previously indicated, the main valve 5S is a sleeve type valve common in the art of subsurface iluid operated pumps and is reduced in diameter near its lower end to provide a downwardly facing shoulder |112 which is in constant uid conmmunication with the vertical bore 84 previously described. The lower end 11.4 of the main valve 58 has a plurality of spaced projections 115 thereon for contacting the lower end of the valve chamber 83 and provides a downwardly facing area in constant communication with the vertical bore 86 previously described.

A plurality of ports 116 are formed radially through the central portion of the main valve 58 in positions to mate with the ports 110 at the upper end of passageway 92 in one position of the -rnain valve, as will be described. Also, a relatively large circumferential groove 117 is formed in the outer periphery of the main valve in upwardly spaced relation from Ithe ports 116 to control the iiow of fluid from the ports i110 to a discharge port 118 formed radially through the cylinder head 23 in another position of the main valve. It will also be noted that the -rnain valve 58 is of such a length that the upper end thereof is below the por-ts but above the ports 102 when the main valve is in its lower position as illustrated in FG. l to provide communication between the inlet 108 and the passageway 90 leading to the lower face of the engine piston 30.

When the main valve 58 and the pilot valve 60 are in their lower positions as illustrated in FIG.. l, power iluid is directed from the inlet 103 .through the ports 100i and passageway $0 to the lower face of the engine piston 30 to provide an upstroke for the engine. Simultaneously, power fluid is exhausting from the upper end of the engine cylinder 26 through the passageway 92, ports 110, groove 117 and port 1.118. At this same time high pressure power huid is in communication with the upper end of the pilot valve y60 through the horizontal bore 98 to retain the pilot valve in its lowermost position. Also, the downwardly facing area 112 is in communication with exhaust pressure through the hores S4 and 62, -the bore 73 and groove 76 and through the horizontal bore 80, such that the high pressure huid acting on the upper end of the main valve 58 will retain the main valve in its lowermost position.

When the engine piston 30 approaches` the upper end of its upstroke, the nut 70 in the upper end of lthe tube 40 contacts the nu-t 74 on the pilot valve 60 to mechanically shift the pilot valve 60' upwardly in its valve chamber 62 which removes the groove 76 in the pilot valve from communication with the horizontal bore 819. This upward movement of the pilot valve 60 places the groove 87 in communication with the groove 76 and bore 78 to e direct high pressure power Huid from the lower end of the main valve chamber through the bore 84 against the downwardly facing area l112 of the main valve 5S to shift the main valve upwardly until it contacts the lower end of the adapter 106. Upon upward shifting movement of the main valve 58, the inlet 108 is placed in communication with the passageway 912 through the ports 116 and ports to impose high pressure power uid on the upper face of the engine piston 30 and reverse the motion of the engine piston for a down stroke. Simultaneously, power fluid is exhausted from the lower end of the engine cylin- 7 der 26 through the passageway 96, ports 162, groove 117 and exhaust port 118.

Near the lower end of the down stroke of the engine piston 30, the nut '70 in the upper end of the tube 4@ contacts the lower head 72 on the trip rod 68 to mechanically 'move the pilot valve 60 back downwardly to its lowermost position illustrated in FIG. 1. The downwardly facalong with a pump piston assembly generally designated by reference character 128. The upper end of the pump cylinder section 122 is connected to the lower end of the engine cylinder 26 by means of a tubular middle plug 130 telescoped over the connecting rod 38. Suitable packing 132 is held in the middle plug 131B in sealing relation around the connecting rod 38 by a packing nut 134 to prevent leakage of fluid between the engine cylinder' 26 and the pump cylinder 120.

The pump piston assembly 123 comprises an upper piston head 136 slidingly sealed by piston rings 158' in an insert 140 threadedly secured to the adapter 126 and extending upwardly throughout the major portion of the length of the cylinder section 122. It may also be noted here that exhaust ports 142 are formed in the upper end portion of cylinder section 122 immediately below the middle plug 130 but above the insert 149. A lower piston head 144 is slidingly sealed in the lower cylinder section 124 by suitablerpiston rings 146 and is connected to the upper piston head by a tubular or hollow rod 148. Suitable packing 150 is retained in the adapter 126 by a packing nut 152 to provide a seal around the hollow rod 148 and prevent a direct transfer of tluid between the insert 140 and the lower cylinder section 124.

A `standing valve assembly, generally designated by reference character 154, is secured to the lower end of the cylinder section 124 to control the flow of well iluids into the pump end 24 and form, with the lower portion of the cylinder section 124, a lower pump chamber 156 below the piston head 144. The standing valve assembly 154 comprises a tubular Valve body 158 threadedly secured in the lower end of the pump cylinder section 124 and having a Valve stop 160 inV the upper end thereof. A valve'seat 162 is secured in the valve body 158 to receive a downwardly closing and upwardly opening standing valve member 164 having a downwardly extending stem 166. A tubular guide 168 is preferably formed in the valve seat 162 to slidingly receive the valve stem 166 and retain the valve head 164 centered with respect to the seat 162'. A seating shoe 167 is threaded into the lower end of the valve body 158 to retain the valve seat 162 in operating position. As it is well known in the art, the shoe 167 facilitates the seating of the pump u uit in a well installation. Also, the seating shoe 167 forms a well fluid inlet 170 for the pump unit. y

The lower pump piston head 144 has a bore 172 extending therethrough providing communication between the lower pump chamber 156 and the hollow rod 148. Also, a bleed port 174V extends through the lower piston head 144 from the upper face of the piston head to the bore 172 to provide communication between the upper and lower faces of this piston head. A spring-loaded check valve 176 is suitably supported in the piston head 144 and intersects the bleed port 174 to prevent a flow of fluid upwardly through the bleed port but provide a downward flow of fluid through the bleed port. Thus, any iluids which may be trapped in the lower pump cylin der section 124 between the piston head 144 and the adapter 126 can bleed downwardly through the port 174 and around the valve 176 into the lower pump chamber 156, such that the piston assembly 128 may complete an upstroke.

The upper pump piston head 136 is tubular in form and has a valve seat 178 secured therein by means of a tubular adapter 180 secured in the lower end of the piston 136 and around the upper end of the hollow rod 148. It will also be noted that ports 182 are formed in the extension 180 to provide constant communication between the hollow rod 148 and an annular pump chamber 184 formed in the insert 1411 between the lower end of the piston head 136 and the adapter 126. An upwardly opening and downwardly closing traveling valve head 186V is positioned in the upper piston head 136 in a position to mate with the valve seat 178. t will be apparent that when the valve head 186 is seated on the seat 178, downward flow of the fluid through the piston head 136 is prevented. On the other hand, the valve head 186 is free to move upwardly away from the valve seat 178 in response to an upwardly directed pressure dif# ferential to allow an upward flow of lluid through the piston head 136. A Valve stem 188 extends downwardly from the valve head 186 and is slidingly received in a tubular guide 19t) formed inside or" the valve seat 178. Ports 192 are formed in the upper end portion of the upper piston head 136 to provide communication between the inner bore of the piston head and the insert 14) above the upper piston head.

The complete operation of the pump unit 20 is best followed by reference to the schematic illustration of FIG. 3. With the main valve 58 in the upstroke position as illustrated in FIG. 3, high pressure power fluid from the inlet 168 is directed through the main valve chamber, passageway 90, adapter 42, tube 40 and ports 36 in the lower end of the engine cylinder 26 to act on the lower face of the engine piston 30. Simultaneously, power fluid is exhausted from above the engine piston 30 through the passageway 92, main valve chamber and port 118 to a pressure lower than the power lluid being fed through the inlet 108. As will be readily understood by those skilled in the art, the port 118 will normally be in communication with the production column to mingle with well lluids being produced by the pump end24. However, the power fluid exhausting through port 118 may be conveyed to the top of the well separately from the produced well lluids if desired.

The engine end 22 obviously drives the pump end 24 in a reciprocating motion by reason of the connection of the connecting rod 38 to the engine piston 30 and the pump piston assembly 128. On the upstroke of the pump piston assembly 128, well l'luids are dra'wn upwardly through the inlet 170 and the standing valve assembly 154 into the lower pump chamber 156. It will also be observed that well lluid is drawn on upwardly through the hollow rod 148 and ports 182 into the upper pump chamber 184. Simultaneously, -any lluid standing in the upper pump cylinder 122 above the upper pump piston head V136 will provide a differential pressure in a downward direction across the traveling valve 186 to retain the traveling -valve 186 closed. Also, this uid in the upper end of the upper pump cylinder section l122 will be forced outwardly through the ports 142 into the production column `and thence to the top of the well. As

- previously indicated, any fluids trapped in the lower pump cylinder section 124 above the lower pump piston head f 144 may be bled downwardly through the bleed port 174 4and around the check valve 176 into the lower pump chamber 156 to allow the pump unit to make la complete upstroke.

At the upper end of the upstroke of the pump unit 20, i

the main valve 58 is shifted in a manner previously described to provide communication between the inlet 108 and the passageway 92, such that high pressure power fiuid willbe fed to the upper end of the engine cylinder 26 to react ina downward direction across the upper face of the engine piston 30. Simultaneously, power fluid standing in the engine cylinder 26 ybelow the engine piston 30 will be forced upwardly through the ports 36, tube 40, adapter 42, passageway 90 :and main valve 58 to the exhaust port 1,18, such that the engine piston 30 will be driven in la downward direction.

During the downstroke of the pump piston assembly 128, the piston assembly imposes a downwardly directed pressure diiferential across the standing valve 154 to close the inlet 170. Well fluid standing in the lower pump chamber 156 will tbe forced upwardly through the hollow rod 148 and the well fluid standing in the upper pump chamber 184 will be forced through the ports 182 into the interior of the upper piston head 4136 Ialong `with the well fluids forced from the lower pump chamber 156. These upwardly moving well uids impose an upwardly directed pressure diierential across the traveling -valve 186 to open the traveling valve 186 and provide la .further flow of these well uids through the ports i192 into the upper end of the upper pump cylinder section 122. It will `also be noted that since well fluids are -forced from both of the pump chambers 156 4and 184, atleast a portion of these well fluids will `be forced on through the upper end of the upper pump cylinder section 122 through the ports 142 into the production column, `depending upon the relative sizes of the piston heads 136 `and 144.

At the end of the down stroke of the pump unit 20, the main valve 58 is again shifted in a manner previously described, such that high pressure power uid is again directed to the lower face of the engine piston 30 to initiate and continue the upstroke of the pump unit.

In briefly reviewing the pump unit 20 illustrated in FIGS. 1 through 3, it will be observed that the engine end 22 is what m-ay be considered a double acting engine wherein high pressure power uid is alternately directed `to the upper and lower faces of the engine piston by means of a four-way valve positioned in the cyl-inder head. With this type of engine, the maximum force may be applied in both the up land down strokes of the engine and the exhausting power fluid may be retained separately from iwell fluids if desired. The pump end 24 is what has been called herein a complex pump having two communicating pump chambers along with a single standing valve assembly and -a single traveling valve assembly.

It will be observed that both pump chambers are filled on the upstroke of the pump unit which reduces the forces resisting downward movement of the pump piston assembly 128 yand therefore decreases the amount of compressive `forces imposed on the connecting rod 38. In the complex pump end illustrated in FIGS. l through 3, the upper piston head 136 is smaller in diameter than the lower piston head 144 to accommodate the pump unit 20 to a well having a relatively high capacity or production. This combination of pump piston heads also provides a substantial pumping 'action on the downstroke of the pump to provide a resulting pumping action resembling a double lacting pump, without the complex valving system required in Ya double acting pump. In fact, the capacity of the pump end 24 is larger than the capacity of a similarly sized double acting pump, since no portion of the lower pumping chamber 156 is occupied -by `a rod member as is at least usually the situation in double acting pumps.

As indicated in the forepart of this specification, a subsurface fluid operated pump .may be either an insert type or `a Ifree pump type. The pump illustrated in FIGS. 1 through 3 and previously described is `an example of an insert type pump unit having ya simple engine and complex pump end which necessarily requires the use of a rather small string of tubing extending from the pump unit to the top of the well for directing high pressure power iiuid downwardly to the pump unit. A pump unit having a simple engine end and complex pump end but adapted -for use as a free pump, is illustrated schemati- 10 cally in FIG. 4 and designated generally by reference character 200.

The pump unit 200 generally comprises a simple engine end 202 and a complex pump end 204 interconnected by a middle plug 206 in tandem relation. The engine end 202 comprises a cylinder 208 extending upwardly from the middle plug 206 and having the head 210 on the upper end thereof. A suitable iis-hing neck 212 is formed on the upper cylinder head 210 to facilitate recovery of the pump unit 200 by a Wire line or the like, as is well known in the art. Ports 214 are formed in the lower end portion of the engine cylinder 208 immediately above the middle plug 206 for directing power fluid into the engine cylinder 208 from the well tubing (not shown) in which the pump unit 200 is seated. A seating ring 215 is carried around the middle plug 206 to engage the tubing in which the pump unit is seated to direct the high pressure power iluid only through the ports 214 and seal off the tubing around the pump end 204. An engine piston 216 is reciprocally disposed in the engine cylinder 208 and is provided with a three-way main valve 218 therein. The main valve 218 may be of any suitable type, such as shown in FIG. 1 of U.S. Patent No. 2,943,576, to control the flow of uid through ports 220 and 222 and through a hollow connecting rod 224 depending from the engine piston 216 in communication with the valve chamber in which the valve 218 is disposed.

The hollow connecting rod 224 extends downwardly from the engine piston 216 through suitable packing 226 in the middle plug 206 into connection with the pump piston assembly generally designated by reference character 228. The pump piston assembly 228 comprises hollow upper and lower piston heads 230 and 232 interconnected by a hollow rod 234. The upper pump piston head 230 is reciprocally disposed in a pump cylinder 236 depending from the middle plug 206. The lower pump piston head 232 is of a smaller diameter than the upper piston head 230 and is reciprocally disposed in a pump cylinder 238 interconnected to the lower end of the pump cylinder 236 by an adapter 240. The hollow rod 234 extends through the adapter 240 and is slidingly sealed therein by suitable packing 242 to prevent direct communication between the two pump cylinders. The standing valve 244 of the pump unit 200 is positioned at the lower end of the lower pump cylinder 238 and the traveling valve 246 of the pump unit is carried in the upper piston head 230. Thus, the complex pump end 204 is provided with a lower pump chamber 248 between the lower pump piston head 232 and the standing valve 244 and is provided with an upper pump chamber 250 between the upper piston head 230 and the adapter 240. It will also be noted that the upper pump chamber 250 communicates with the upper end of the hollow rod 234 immediately below the traveling valve 246 through ports 252 formed either through the upper end portion of the rod 234 or through the lower end portion of the upper piston head 230.

A seating shoe 254 is secured to the lower end of the lower pump cylinder 238 for supporting the standing valve 244 and to form an inlet 256 for the pump unit. A jacket 258 extends from the seating shoe 254 upwardly around the lower pump cylinder 238 into connection with the tubular adapter 240. The jacket 253 provides an annular passageway 260 around the length of the lower pump cylinder 238. One or more ports 262 provide communication between the lower end of the annular passage 260 and the inlet 256 below the standing valve 244, and suitable ports 264 provide communication between the upper end of the passage 260 and the upper end of the pump cylinder 238. Thus, the upper end of the lower pump cylinder 238 and the upper face of the lower piston head 232 are in constant communication with Well iuid pressure existing in the inlet 256 to minimize the downward torce imposed across the lower piston 11 head 232 and facilitate the upstroke of the pump unit 288, as will more clearly hereinafter appear.

With the main valve 218 of the pump unit 280 positioned as illustrated in FIG. 4, the high pressure fluid directed through vthe inlet'ports 214 will act across the lower face of the engine piston 216 and force the engine piston 216 on an upstroke. Simultaneously, power fluid standing in the upper end of the engine cylinder 288 is directed downwardly through the port 222 and through the main valve 218 into the hollow connecting rod 224. This exhausting power fluid is directed across the upper end of the traveling valve 246 and then upwardly through ports 266 into the upper'end of the upper pump cylinder 236. VIt will be apparent that the exhausting powery uid flowing downwardly through the hollow connecting rod 224 will retain the traveling valve 246 closed. Also, this exhausting power fluid is directed from the upper end of the upper pump cylinder 236 through ports 268 into the production column extending to the top of the well in which the pump unit 200 is seated.

The upward movement of the engine piston 216 is obviously transmitted through the hollow connecting rod 224 to move the pump piston assembly 228 on an up- .stroke at the same time.

During upward movement of the pump piston assembly 228, well fluids are drawn upwardly through the inlet 256 and around the standing valve 244 into the lower pump chamber 248. Simultaneously, well fluids are drawn from the pump chamber 248 upwardly through the hollow rod 234 and through the ports 252 into the upper pump chamber 258. It will be apparent that since the traveling valve 246 is closed on the upstroke of the pump piston assembly, suction will be created both in the upper and lower pump chambers 250 and 248 for opening of the standing valve 244 and lling these pump chambers with well iiuids. It may also be noted that the upper end of the lower pump cylinder 238 is then at lower well lluid pressure through the ports 264, passageway 266 and ports 262 as previously described, such that virtually no pressure differential will be imposed across the lower pump piston head 232 during the upstroke and the power required for moving the pump piston assembly 22S on upstroke is retained at a minimum.

At the upper'end of the upstroke of the pump unit 280, the main valve 218 is shifted as is common in the art to Y direct high pressure power liuid from the lower end of connecting rod 224 is closed by the main valve 218.

On the downstroke of the pump piston assembly 228, a downwardly directed pressure differential is imposed across the standing valve 244 to close this valve; and, an upwardly directed pressure differential is imposed across the traveling valve 246 to open this valve. Therefore,

well uids standing in the pump chambers 248 and 250 are exhausted upwardly through the hollow rod 234 and inwardly through the ports 252 aroundthe traveling valve 246 and through the ports 266 into the upper pump cylinder 236 above the upper pump piston head 238. A portion of these well uids exhausted from the pump cham- V'bers 248 and 25) is directed on outwardly through the ports 268 into the production column, and it will be apof the pump cylinder 238 is merely lled with well fluids on the downstroke.

Complex Engine End rl`he pump unit 388 illustrated in FIGS. 5 and 6 is another free pump type of unit and generally comprises a complex engine 302 and a simple pump end 304 connected in tandem relation by a middle plug 306. The engine end 302 comprises upper and lower engine cylinder sections 388 and 318 interconnected by a tubular adapter 312 to contain the engine piston assembly generally designated by reference character 314 and which will be described in detail below. The lower end of the lower engine cylinder section 310 (FIG. 6) is threadedly connected to the upper end of the middle plug 386, and the upper end of the upper engine cylinder section 388 (PEG. 5) is closed by a cylinder head 316. A tubular adapter 318 is threadedly secured in a counterbore 328 in the upper end of the cylinder head 316 to support a downwardly facing swab cup 322 at the upper end of the pump unit. A hollow nose cone 324 is threadedly secured a the upper end of the adapter 318 and is utilized to hold a retaining ring 326 downwardly against the swab cup 322 for securing the swab cup 322 in a lixed position on the adapter 3l8. A shing neck 328 is formed on the upper end of the nose cone 324 to facilitate recovery of the pump unit 388 as will be readily understood by those skilled in the art.` It will also be observed that ports 338 and 332 are formed in the nose cone 324 and the adapter 318 to allow the downward ilow of high pressure power iluid through the nose cone and adapter assembly for a normal operation of the pump unit 388.

A downwardly facing valve seat 334 is formed in the tubular adapter 318 above the ports 332 and a valve head 336 is reciprocally disposed in the adapter 318 in a position to mate with the valve seat 334. A suitable spring 338 is seated inthe counterbore 320 and constantly urges the valve head 336 upwardly toward the seat 334. Thus, the valve head 336 will be closed when no fluid pressure is acting downwardly across the valve head, such that any fluid pressure uid acting upwardly through the ports 332 will be prevented from llowing through the nose cone 324 and will react across the downwardly facing swab cup 322 to facilitate the removal of the pump unit380 from a well installation as a free pump. However, the valve head 336 will be moved downwardly against the action of the spring 338 when a downwardly directed pressure dilferential is exerted across the valve head to allow the ow of high pressure fluid downwardly `through the nose cone 324 and then outwardly through the ports 332 for a normal pumping operation of the pump unit 380. The valve head 336 isV guided and retained aligned with the valve seat 334 by means of a downwardly extending stern 340 sliding in a counterbore 342 in the head 316 and by a stem 344 sliding inra reduced diameter portion of the nose cone 324.

Ports 346 and 348 are formed in the lower end of the upper engine cylinder section 308 and in the upper end of the middle plug 306, respectively, to feed high pressure power fluid ilowing downwardly through the nose cone 324 and adapter 318 around the pump unit 380 intol the lower ends of the engine cylinder sections. Thus, during a normal operation of the pump unit 380, high pressure power fluid is constantly directed into the lower rod 356 is in constant communication with the upper end of the upper engine cylinder section 308 above the upper piston head 350. Suitable packing 358 is secured in the adapter 312 by means of a retainer ring 360 threadedly secured in the upper end of the adapter to provide a sliding seal around the rod 356 and prevent the direct transfer of fluid between the lower end of the upper engine cylinder section 308 and the upper end of the lower engine cylinder section 310. The lower end of the hollow rod 356 is connected to the lower engine piston head 352 by tubular connector 362 to provide simultaneous reciprocation of the engine piston heads 350 and 352.

The valve mechanism generally designated by 364 is a three-way valve of the type illustrated in FIG. l of U.S. Patent No. 2,943,576 and generally comprises a piston-type valve 366 (FIG. 6) slidingly supported in a piston extension 368 between valve seats 370 and 372. The vve 366 has an extension 374 extending downwardly therefrom through the valve seat 372 which is contacted by a harness mechanism 376 for shifting the valve upwardly at the end of the downstroke `of the engine piston assembly in the same manner as disclosed in the U.S. Patent No. 2,943,576. A restrictive diameter sleeve 378 (FIG. is slidingly supported in the upper valve seat 370 for shifting the valve `366 downwardly at the end of the upstroke of the piston assembly in the same manner as in U.S. Patent No. 2,943,576. It will also be noted that the sleeve 37 S is urged upwardly by a spring 380 to normally retain the sleeve 378 out of contact with the upper end of the valve 366.

A valve shifting mechanism 382 is carried in the tubular connector 362 above the engine piston head 352 for contacting the sleeve 378 and shifting the valve 366 downwardly at the end of the upstroke of the engine piston assembly, rather than by contact of the sleeve 378 with the upper end of the engine cylinder as in U.S. Patent No. 2,943,576. The valve shifting mechanism 382 comprises a head 384 slidingly secured in the tubular connector 362 as illustrated in FIGS. 5 and 5A. A pin 386 extends through the head 384 and through slots 388 in opposite sides of the connector 362. The pins 386- extend outwardly from the connector 362 a sufiicient distance to engage the lower end of the tubular adap-ter 312 near the end of the upstroke of the engine piston assembly. Therefore, the upward movement of the head 384 will be stopped prior to the end of the upstroke of the engine piston assembly to contact the upper end of the sleeve 378 and shift the valve 366 downwardly in substantially the same manner as illustrated and described in U.S. Patent No. 2,943,576.

The valve mechanism 364 controls the flow of fluid through a passageway 390 extending from ports 392 in the tubular connector 362 downwardly around the sleeve 378, the upper valve seat 370, the valve chamber of the valve member 366, through the lower valve seat 372 and around the chamber of the valve extension 374 to a chamber 393 at the lower end of the piston extension 368. of fluid through `a second passageway 394 extending from the ports 392 upwardly into the tubular connector 362, then downwardly through the sleeve 378, the upper valve seat 370 and then through ports 396 which communicate with the valve chamber receiving the valve 366 and the engine cylinder section 310 below the engine piston head 352. It is not believed necessary to describe the detailed operation of the valve mechanism 364 since this operation is the same as that disclosed in U`.S. Patent No. 2,943,576. It is believed suflicient to note that when the valve mechanism 364 is in its upper position as illustrated in FIG-S. 5 and 6, power fluid standing in the engine cylinder section 310 above the lower piston head 352 is directed downwardly through the ports 392 and the passageway 390 to the exhaust chamber 393 while fluid is prevented from flowing upwardly through the passageway 394, such that high pressure power fluid is applied across the lower face of the piston head 352. In the opposite position of the valve mechanism 364, power fluid is prevented frorn flowing downwardly through the passage- The valve mechanism 364 also controls the 4llow r way 392 through the lower valve seat 372 and power fluid is directed upwardly through port '396 and the passageway 394 and ports 392 to act downwardly across the upper end of the piston head 352.

As shown in FIG. 6, a hollow connecting rod 398 is threadedly secured in the lower end of the engine piston extension 368 in communication with the exhaust chamber 393 and extends downwardly through the middle plug 306. Suitable packing 400 is held in the middle plug 306 around the rod 398 by a suitable retainer 402 to prevent the leakage of fluid between the engine cylinder section 310 and the pump end 304. The lower end of the hollow connecting rod 398 is threadedly secured to a hollow pump piston 404 having -a traveling valve 406 therein. The traveling valve 406 is adapted to mate with a valve seat 408 threadedly secured in the lower end of the pump piston 404 and is held concentrically with respect to the seat 408 by a stem 410 extending through a guide 412 formed in the seat 408. -A valve stop 414 is formed in the piston 404 a short distance above the traveling valve 406 to limit the opening movement of the traveling valve. A chamber 4116 is formed above the stop 414 and communicates with the upper end of the pump piston 404 through ports 416 extending at an angle through the pump piston to the interior of the pump piston.

The pump piston 404 is slidingly sealed in a pump cylinder 418 by suitable piston rings 420 to provide a pumping action as will be described. The upper end of the pump cylinder 418 is secured to the middle plug 306 by a tubular adapter 422 having radial ports 424 therein which form exhaust ports for pumped well fluids and exhausting power fluid. The adapter 424 also functions to hold a seating ring 426 around the middle plug 306 against a retaining ring 428. The seating ring 426 is designed to engage the walls of a pump cavity (not shown) in which the pump unit 300 is positioned to separate high pressure fluid above the middle plug from the lower pressure below the middle plug.

A standing valve body 430 is threadedly secured to the lower end of the pump cylinder 418 and contains an upwardly facing .valve seat 432 adapted to receive a standing valve 434. The valve 434 is retained concentrically with respect to the seat 432 by a stem 436 slidingly fitting in a tubular guide 438 formed in the valve seat. It will also be noted that upward movement of the valve 434 is limited by a suitable stop 4401 formed in the upper end of the valve body 430. A seating shoe 442 is threadedly secured in the lower end of the valve body 430 to retain the valve seat 432 in operating position and to facilitate the seating of the pump unit 300 in a pump cavity. The shoe 442 also forms the well fluid inlet 444.

The overall operation `of the pump unit 300` is best followed by reference to the schematic illust-ration in FIG. 7. As previously indicated, high pressure power fluid is constantly fed to the lower end of each of the engine cylinder sections 308 and 310 through the ports 346 and 348, respectively. With the three-way valve mechanism 364 in the position illustrated in FIG. 7, power fluid standing in the upper end of the upper engine cylinder section 308 above the engine piston head 350 is directed downwardly through the hollow rod 356 and then outwardly through the slots 3881 into the upper end of the lower engine cylinder sec-tion 310. This exhausting power fluid, along with the power fluid standing in the upper end of the cylinder `sect-ion 310 isdirected downwardly through the ports 392, the passageway 390 and the valve mechanism 364 into the hollow connecting rod 398. This power fluid is then funther exhausted through the ports 416 in the upper end of the pump piston 404 into the upper end of the pump cylinder 418 for discharge through the ports 424. Thus, the upper face of each of the engine piston heads 350' and 352 is exposed to a pressure lower than the pressure of the power fluid directed through the ports 346 and 348,

adottata such that the engine piston assembly will be directed on an upstroke.

The pump piston 494 will obviously be moved on an upstroke simultaneously with the engine piston assembly to draw well fluids upwardly through 4the inlet 444 and around the standing valve 434 into the lower end of the pump cylinder 418. Simultaneously, liuid standing in the upper end of the pump `cylinder 418, as well as the exhausting power lluid previously described, will be directed outwardly through the ports 424 into the production column. It will be apparent that the traveling valve 406 will be closed on the upstrolce by reason of the downwardly acting pressuredilerential thereon.

Near the end of the upstroke of the pump unit 300, the valve shifting mechanism 382 contacts the :tubular adapter 312 to initiate the shifting of the valve mechanism 364 to -its opposite position where the valve mechanism provides communication between the passageways 394- and 390 and, in effect, closes oli the upper end of the hollow connecting rod 398i. in this latter position of the valve mechanism 364, high pressure power Huid being ted to the lower end of the engine cylinder section 310 yis directed through the ports 396, passageway 394, valve mechanism 364, passageway 390 `and ports 392 into the upper end of the cylinder 310 to act in a downward direction across the lower engine piston head 352. This power lluid is also directed through the slots 388 and upwardly through the connecting rod 356 into the upper end of the upper engine cylinder section 308 to act downwardly lacross the upper tace of the upper engine piston head 350. A's a result, both the upper and lower -faces of each of the piston heads 350 and 352 are exposed to the action of high pressure power uid. However, since the upper lface of the upper engine piston 350 has an area larger than the exposed area of the lower yface of the piston head 350, by reason of the hol- -low rod 356, the net hydraulic force on the engine piston assembly is in a downward direction to move the piston assembly on a downstroke.

On the downstroke of the pump piston 404, the standing valve 434 is closed and the traveling valve 406 is opened to provide a transfer of well tluids standing in the lower end of the cylinder 418 through the piston 404 to the upper end of the cylinder 418. It will also be noted that a volume of these well uids equal to the volume occupied by the connecting rod 398 in the pump cylinder 418 will be forced through the ports 424 into the production column to provide a minor production of fluid on the downstroke. However, since the major portion of the pumping action of the pump 302 takes place on the upstroke, the pump 304 is normally considered a single acting pump.

At the end of the `downstroke of the pump unit 300 the valve mechanism 364 is shifted back to the position illustrated in FlG. 7 in the same manner as the shifting of the Valve mechanism in U.S. Patent No. 2,943,576 to reverse the movement of the engine piston assembly and provide an upstroke.

In reviewing the construction and operation of the pump unit 300, it will fbe observed that the pump unit is a free-type pump unit `comprising a complex engine end 302 and a simple pump'end 304. This combination is particularly adapted for producing a well having normal Production capacity but relatively high horsepower requirements. The engine piston yassembly 314 provides two sets of working lareas facing in opposite directions to provide a substantial increase in horsepower output compare-d with a simple engine end. The lower -faces of the upper engine piston head 350 and the lower faces of the lower pistn head 352 and piston extension 368 all obviously face in Ithe same :direction and have a combined area larger than the cross-sectional area of the engine cylinder sections 308 or 310. The upper ends of the upper piston head 350 `and lower piston head 352 have `still a larger combined area to provide a downstroke of the unit when both the upper and lower faces are exposed to the same high pressure fluid.

The pump unit 500 illustrated in FIG. 8 is provided herein to show an insert-type pump having thel same general combination of a complex engine end and simple pump end. In fact, the pump end of 4the pump unit 500 may be the same construction as the pump end 304 of the pump unit 308 and is so illustrated in FIG. 8. The engine end 502 of the pump unit 500 comprises an engine cylinder 504 connected to the upper end of the pump cylinder 418 by means of a suitable middle plug 506 and having the 'same diameter Ias the pump cylinder 418. A suitable seating ring 508 is secured around the middle plug 506 to seat the pump unit 500 in a pump cavity as illustrated in U.S. Patent No. 2,- 917,000'.

An engine piston assembly 510 is reciprocally disposed in the engine cylinder 504 `and comprises vertically spaced heads 512 and 514 interconnected by a rod .assembly 516. The upper piston head 512 is smaller Iin diameter than the lower piston head 514 and is re'- ciprocally disposed in an insert 518 depending from the upper cylinder head 520. The lower end of the insert 518 is provided with a head portion 522 sealed by a packer 524 to the inner periphery of the engine cylinder 504 and sealed by a packer 526 around the rod assembly 516. I't will also be notedth-at the insert 518 provides an annular passageway 528 communicating with the lower face of the piston head 512 through ports 530.

The rod assembly 516 provides an inner passageway 532 and an outer, annular passageway 534. The inner passageway 532 communicates through ports 536 with the upper end of the insert 51,8. Passageway 532 also communicates through a passageway 538 in the lower head 514 with the upper end of the piston head 514. Thus, the upper face of the upper engine piston head 512 and the upper face of the lower engine piston, head 514 are in constant communication. The annular passageway 534 communicates with the lower face of the upper piston head 512 through ports 540 and with the lower face of the lower piston head 514 through ports 542.

A three-way valve mechanism 544 of any suitable type, such as illustrated in FIG. 14 of U.S. Patent No. 2,943,576 is supported in the upper cylinder head 520 and actuated by the piston assembly 510 through a'trip rod 546. The valve mechanism 544 is arranged for shifting at the upper and lower ends of the stroke of the pump unit 500 by Contact of the trip rod 546 by the engine piston assembly 510 in a manner common to the art. An inlet passageway 548 extends through the cylinder head 520 into constant communication with the passageway 528 formed around the insert 518 and with one side of the valve chamber containing the valve mechanism 544. An outlet passageway 550 is also formed in the cylinder head 520 and extends from the valve mechanism 544 to the exterior of the pump unit. Another passageway 552 is formed in the cylinder head 520 between the valve mechanism 544 and the upper end of the insert 518 to control the low of luid to and from the upper faces of the engine piston heads, as will be described.

With the valve mechanism 544 in the position shown in FIG. 8, the upper face of the upper engine piston head 512 is exposed to exhaust lluid pressure through the passageway 552, valve mechanism 544 and exhaust passageway 550. Simultaneously, the upper face of the lower piston head 514 is also exposed to exhaust fluid pressure through passageway 538, passagewayV 532 and ports 536. At the same time, high pressure uid is directed through the inlet 548, annular passageway 528 and ports 530 against the lower face of the upper engine head 512. This high pressure fluid is also directed through the ports 540, annular passageway 534 and ports 542 against the lower face of the lower engine piston head 514. As a result, the engine piston assembly 510 is moved on an upstroke to raise the pump piston 404 and draw in a supply 17 of well fluid around the standing valve 434 of the pump end 304.

Near the end of the upstroke of the pump unit 500, the engine piston assembly 510 contacts the trip rod 546 to shift the valve mechanism 544 in a direction to close the exhaust passageway 550 and open the passageway 552 to the inlet 548. The high pressure power fluid will then be directed through the valve mechanism 544 and the passageway 552 to react in a downward direction across the upper face of the upper engine piston head 512. This high pressure power fluid is also directed downwardly through the ports 536 and the passageways 532 and 538 to react across the upper face of the lower engine piston head 514. Therefore, both the upper and lower faces of both of the engine piston heads are exposed to high pressure fluid. However, since the combined areas of the upper faces of the piston heads 512 and 514 is larger than the combined areas of the lower faces of these piston heads, the piston assembly S10 will be moved on a downstroke. Well fluids standing in the lower end of the pump cylinder 4l8 will, therefore, be directed upwardly around the traveling valve 406 and through the ports 416 into the upper end of the pump cylinder. A portion of these well fluids will also be forced outwardly through the exhaust port 554 in the middle plug 506 into the production column. Near the end of the downstroke of the pump unit 500, the engine piston assembly 510 again contacts the trip rod 546 to shift the valve mechanism 544 back to the position illustrated in FlG. 8 to reverse the movement of the engine piston assembly and provide an upstrolre in the manner previously described.

In brley reviewing the construction and operation of the complex engine end 502 of the pump unit 500, it will be observed that the lower faces of the piston heads l?. and 514 are in constant communication and have a combined cross-sectional area larger than the cross-sec tional area of the engine cylinder 504 to provide a substantial power output on the upstroke of the pump unit. It will also be observed that the upper faces of the piston heads 5l?. and 514 have a combined area larger than the downwardly facing areas of these piston heads since no rod extends upwardly from the upper piston head 512. Therefore, the engine piston assembly 510 provides two sets of working areas facing in opposite directions and each set of working faces has a combined area larger than the cross-sectional area of the engine cylinder. The three-way valve mechanism 544 alternately directs power uid toward and away from the upper faces of the engine piston heads to provide a reciprocation of the engine piston assembly 510 and operation of the pump end 304.

The pump unit 600 shown in FIG. 9 is another illustration of a pump unit comprising a complex engine end 602 and a simple pump end, such as the pump end 304 illustrated in FIGS. 7 and 8 and previously described. The engine end 602 comprises an engine cylinder 604 connected in tandem relation with the pump cylinder 418 through use of a middle plug 506 of the same construction illustrated and described in FG. 8. An engine piston assembly 606 is reciprocally disposed in the engine cylinder 604 and comprises what may be considered upper and lower heads 600 and 610 interconnected by a sleeve 612. The upper engine piston head 608 is an annular shaped member and is provided with a packer element 614 around the inner periphery thereof sealingly engaging an extension 616 extending downwardly into the engine cylinder 604 from the upper cylinder head 618. Y

The extension 616 is provided with an enlarged head portion 620 on the lower end thereof of a size to slidingly and sealingly engage the inner periphery of the sleeve 6l2 which interconnects the engine piston heads 60S and 6M?. The head 620 is positioned in the central portion of the engine cylinder 604 to allow the maximum travel of the engine piston -assembly 606 in opposite directions. Annular passageway 622 extends through the extension 616 from the high pressure power fluid inlet 624 in the head 618 to ports 626 in 'the upper end portion of the extension head 620 to constantly direct high pressure power fluid into the annular space between the extension 6'16 and the engine piston assembly sleeve 612 underneath -tlhe engine piston head 608. It will also be noted that ports 628 are also provided in the upper end portion of the sleeve612 immediatley under the head 608 to direct this power fluid into the lower end portion of the engine cylinder 6014 underneath Ithe lowerl engine piston head 610. A central passageway 630 is formed through the extension 616 from ports 632. `communicating with the lower face of the extension head 620. The upper end of the central passageway 630 communicates through a passageway 634 with the upper end of the engine cylinder 604 above the upper engine piston head 608.

A suitable three-way valve 636, such as the three-way valve illustrated in FIG. l in U.S. Patent No. 2,943,576, is carried Iby the lower engine piston head 610 to control the application of high pressure power uid to the upper faces of the engine piston heads 610 and 60S, as will be described. A port 63S extends from the lower face Vof the engine piston head 616 to the valve 636 and another port 640 ex-tends from the upper `face of the head 610 to the valve 636. A Ithird port 642 associated with the valve 636 communicates with a hollow connecting rod 644 extending from the lower end of the piston 610 through the middle plug 506 into connection with the pump piston 404.

When the three-way valve 636 is positioned as lillustrated in FIG. 9, the port 638 is closed and the ports 640 and 642 are placed in communication. Therefore, the high pressure power fluid being directed underneath the engine piston heads 608 and 60 will be prevented from owing through the chamber containing the valve 636 and will therefore only react in an upward direction across the lower faces of the piston heads 608 and 610. The upper end of the engine cylinder 604 communicates with a lower pressure through the passageways 634 and 630 and the ports 632 with the interior of `the sleeve 612 below the extension head 620. This latter chamber in turn communicates with lower pressure through the port 640, valve 636, port 642, hollow connecting rod 644 and ports 416 in the pump Vpiston 404. Therefore, the high pressure power fluid acting against the lower faces of the engine piston heads 608 `and 630 will move the engine piston assembly 606 in an upstroke and the fluid standing in the engine cylinder 604 above the upper engine piston head 608 and the iiuid standing in the extension 612 above the lower piston head 610 will be directed -or exhausted into `the production fluid column.

When the engine piston assembly 606 approaches the upper end of this stroke, the three-way valve 636 is shifted in the mann-er described in U.S. Patent No. 2,943,576 -to provide communication between the ports 638 and 640 to close the port 642. Therefore, high pressure fluid will flow from the lower end of the engine cylinder 604 through the ports 633, the valve 636 and the port 640 into the chamber directly above the lower engine piston head 6&0. This high pressure power fluid will continue `to ow through the port 632 and passageways 630 and 634 in-to the upper `end of the engine cylinder 604 to react in a downward direction on the upper face of the upper engine piston head 603. Careful inspection of FIG. 9 discloses that the exposed upper faces of the piston heads 60S and 610 has a `combined area larger than the combined `area of the exposed lower faces Iof the engine piston heads by an amount equal to the crosssectional area of the hollow connecting rod 644, such that a net hydraulic force will be imposed in a downward direction on the engine piston assembly when all of these areas are exposed to the same fluid pressure. Therefore, the `engine piston assembly 606 will be moved `on :a downstroke.

VNear the end `of the downstroke of the engine piston assembly 606, the three-way valve 636 is `again shifted to the position illustrated in FIG. 9; whereupon7 the uper faces of the engine piston heads 668 and 61@ are again placed in communication with production column pressure to reverse the movement of the engine piston assembly and provide an upstroke.

In briefly reviewing the construction and operation of the pump unit 690, it will be apparent that the engine piston assembly of the pump unit provides two sets of working areas or faces extending in opposite directions. The combined area `of each of these sets of working faces is larger than the cross-sectional area of the engine cylinder 604 to provide an increased horsepower output for the .engine 6112 compared with a simple engine construction.

to high and lower pressure iluid to provide the reciprocation of the pump unit.

Combination Complex Engine and Pump Ends FIGS. 10, ll and l2 structurally illustrate a pump unit 7u() comprising a complex engine end 702 and a complex pump end 7114. The engine end 7152 generally comprises upper randv lower cylinder sections 706 land 708` and upper and lower engine piston heads 710 and 712 reciprocally disposed in the respective cylinder sections and interconnected by a hollow rod 714 for simultaneous movement. rThe cylinder Isections 706 and 708` are threadedly interconnected in tandem relation by a tubular adapter 716 having a packer element 713 therein'for sealingly engaging the engine piston assembly and preventing direct communication between the two engine cylinder sections. The packing element 718 is retained in operating position by a suitable retainer nut 720. The upper cylinder head V722 at the upper end =of the cylinder section 706 is tubular in form and is :adapted at its upper end for connection with a tubing 724 extending from the top of the well in which the pump unit is disposed ifor directing high pressure -power fluid into the pump unit.

The upper engine piston lhead 716 is provided with suitable piston rings 726 to slidinglywseal the head in the cylinder section 7616 and is tubular in form to provide a bore 728 extending vertically through the central portion thereof. Y A tube 739 is threadedly secured in the upper end `of the bore 728 and extends upwardly through the cylinder head 722 `to form an inlet for high pressure power fluid being fed to the pump unit. It will also be noted that a pac-ker `element 732 is secured in the cylinder head 722 Varound the tube 730, and the packer element is held in operating position by a retainer nut 734i. A port 736 extends transversely through the piston head 710 directly below the piston rings 726 to constantly direct high pressure power iluid against the lower face of the piston head 710, as will be more fully described. A chamber 738 is formed in the pistonhead 71d a short distance below the port 736 and communicates with the upper face of the piston head 710 through a vertical bore 740 extending alongside the central bore 72S. The chamber 738 also communica-tes with a tube 742 secured in a coun-terbore at the lower end of the Vertical bore 728 and extending downwardly through the packer element 718 of the adapter 716. The tube 742 terminates below the adapter 716 in open communication with the upper end of the engine cylinder section 7 68. Thus, the upper ends of the cylinder sections 706 and 7&8 are in constant communication Y through the bore .740, chamber 735 and tube 742,

As illustrated in both FIGS. 10i and 11, the hollow rod 714 interconnecting the engine'piston heads 710 and 712 extends inside `of the tube 742 and provides a continuation of the passageway .formed bythe 'bore 728 in the upper piston Vhead 710. The lower end of the hollow rod'714 is connected to the upper end of the lower engine piston head 712 by means of asuitable adapter 744 and communicates with a chamber 746 formed directly under the adapter 744-. The chamber 746 in turn communicates with a verticd bore 748 extending to the lower end of -t-he engine piston 712 to provide continuous communication between the lower ends of the engine cylinder 'sections 766 and 76S through the port 736 and bore 728 in the upper engine piston 71), the hollow rod 714, the chamber 746 and the bore 748 in the lower piston head 712. rFhus, the lower ends of both of these engine cylinder sections are constantly exposed to high pressure power iiuid from the inlet tube 730. Suitable piston rings 751B are carried by the lower piston head 712 in sliding and sealing engagement with the cylinder section 708 in a manner common to the art. Y

A three-way valve mechanism, generally designated by reference character 752, ris carried @by the' lower engine piston head 712 to control the flow of fluid from the lower end of the engine cylinder Isection 768 to the upper end of the engine cylinder section 708, yas well as between the upper end of the cylinder section 708 and ia hollow connecting rod 754 extending downwardly from the lower piston head 712 to the pump end 794. The valve mechanism 752 generally comprises a pair of vertically spaced valve seats 756 and 758 secured in the desired positions in a tubular extension 769 extending downwardly from the main body portion of the lower engine piston head 712 and a tubular valve 762 `adapted to alternately seat on the seats 756 and 758. The valve mechanism 752 i1- lustrated in FIG. l1 has the same construction and openation as the valve mechanism illustrated in FIGS. 16 and 17 of US. Patent No. 2,943,576. lt is, therefore, believed necessary only to point out the main structural components in this specification. The upper valve `seat 756 is secured at `the lower end of the main body of the piston head 712 `and extends into 4a bore 764 to `form an anchor for a helical spring 766. A sleeve 768- extends loosely through the bore 764 and the valve seat 746 and is provided withV a ilange 770 near the upper yend thereof to receive the upper end yof the spring 766, such that the sleeve 768 is 'normally retained in Vits upper position with the flange 770in contact with a flange 772 formed in the bore 7 64. Port-s 77 iare formed in the lower end portion of the sleeve 768 and are :alternately opened and closed lby the upper end portion of the valve 762 as the valve 762 moves toward and away from the valve seat 756.

A harness mechanism 776 is carried lat the upper end of the engine piston head 712 Vand is provided with a crossbar or `arm 778` at the lower end thereof to contact the upper end of the valve sleeve 768 and shift the valve .mechanism 752 at the upper end of the upstroke, as in U.S. Patent No. 2,943,576. The harness mechanism 776 is normally retained above the upper end of the sleeve 768 by ia suitable spring 7 80 resting on the upper end of the piston head 712. It will Valso be noted that projections 1 or feet 782 are formed on the upper end of the harness 776 radially outward from the tube 742 for contact with the adapter 716 near the end of the upstroke of the pump unit.

The lower valve seat 758 of the valve mechanism 752V is threadedy secured to the upper end of the hollow connecting rod 754 and is provided with an upwardly facing `seating area 784 to receive the lower end of the valve sleeve 762 when the valve sleeve is in Vits lowermost position. The valve seat 75S is also provided with a projection 786 of a size to be received in the lower end of the valve sleeve 762 in the same manner as in US. Patent No. 2,943,576. An insert 7&8 is positioned in the piston extension 76? `directly above :the main body portion of the valve seat 75S to form aseal around the valve sleeve 762.V and is ccunterbored at its lower end to form a chamber 791i around the valve seating area '7d-4. lPorts 792 :are formed in the valve seat 758 below the seating area 7&6 to provide communication between the interior of the valve sleeve 762 .and the 21 upper end or" the hollow connecting rod 754 when the valve sleeve is raised oil of the seating area 754.

The lower end '794 of the piston extension 715i)l is tapered downwardly and inwardly and is provided with external threads for engagement by a lock nut 796 which presses the end portion 79d of the piston extension tightly around the outer periphery of the hollow connect ing rod 754 and retains the mechanism in assembly. Another helical spring 79S is positioned around the nut 79d to constantly urge the lower harness mechanism Still downwardly to an inoperative position. The lower harness Still comprises a plurality of arms 802 extending alongside the outer surface of the piston extension 76d and having their lower ends curved inwardly to receive the spring 798. The upper ends of the arms 862 are connected by screws Silit to a tubular actuator 8% extending around the valve sleeve 762. The actuator 'Sile has outwardly extending guides 98 extending through slots dltl in the piston extension 769 which allow vertical movement of the harness assembly 89%). The actuator della is of a size to move in and out of a counterbore lill formed in the extension 76h immediately underneath the upper valve seat 75d to restrict the flow of iluid through the ports 774 and control shifting of the valve mechanism 752 at the end of the downstroke as in US. Patent No. 2,943,576.

When the valve mechanism 752 is in the position shown in =FIG. ll, high pressure fluid ilows from the lower end of the engine cylinder section 708 through the slots 8l@ in the piston extension 76d, the ports 77d in the valve sleeve 76S and then upwardly through the valve sleeve 763 into the upper end of the engine cylinder section 70S to provide a downstroke of the pump unit, as will be more fully hereinafter described. Near the end of the downstroke, the lower harness mechanism eil is retarded by a middle plug 814 (FIG. 12) at the lower end of the engine cylinder section '7b3 to move the actuator 3% into the counterbore S12 and shift the hydraulic .forces acting on the valve mechanism 752, such that the valve member 762 is shifted upwardly onto the upper valve seat 756. rlhe upper end of the engine cylinder section 7% is then placed in communication with the hollow connecting rod 754 through the valve sleeve 76S, tubular valve 7 o2, counterbore 79d and ports 7% in the lower valve seat 75S` to provide an upstroke for the pump unit, as will be described. Near the end of the upstroke of the pump unit, the feet '732 of the upper harness 776 contact the lower end of the adapter '716 and retard `:further upward movement of the 'upper harness mechanism. The upper end ot' the valve sleeve 76', is then brought into Contact :with the harness arm 775 for downward movement of the sleeve 768 in the bore 764 of the piston head 7M.. This movement of the valve sleeve 768 shifts the valve mechanism 752 back to the position shown in FIG. ll as explained in detail in U.S. Patent No. 2,943,576.

The pump end 79d illustrated in FIG. l2 comprises two cylinder sections die and Sid containing two pump piston heads 82d and 822-, respectively. The upper pump cylinder section Sid is connected to the lower end of the lower engine cylinder section 76S by means of the middle plug Sie as previously mentioned. The middle plug dlfl is tubular in form and contains a packer element S24 held in `sealing relation around the hollow connecting rod 75d by a retainer nut S26. The middle plug diri is also provided with ports 823 therein extending from a counterbore 330 in the lower end of the plug to the outer surface of the plug for discharge of pumped well fluids and exhausting power lluid to the exterior ot the pump unit, as will be more fully described.

The lower pump cylinder section Sill is connected to the lower end of the upper pump cylinder section @lo by means of a tubular adapter S32 having a counterbore 33d in the lower end thereof. Ports 36 extend upwardly and outwardly through the adapter 32 from the upper end of the counterbore @34 for the discharge of pumped well lluids to the exterior of the pump unit, as also will be hereinafter described.

A standing valve body 84th' is secured to the lower end of the lower pump cylinder section Sll to receive a standing valve i842. The valve S42 cooperates with a valve seat 344i secured in the valve body 84d by means or" a tubular seating shoe 846. lt will be noted that the standing valve .t5-ft2 opens in an upward direction and closes in a downward direction for controlling the flow oi well tluids through the well liuid inlet 848 formed by the seating shoe S46. A valve stem 35d depends from lthe valve dell and is guided by a tubular guide 852 formed in the seat 44 to retain the valve concentric with the seat. lso, a suitable stop 354 `is formed in the upper end of the valve body 46 to limit the upward, opening movement of the valve `Sill The upper and lower pump piston heads 820 and 822 are interconnected by a hollow rod 856 extending through the tubular adapter S32. A suitable packing element 85S is secured in the adapter 832 in sealing relation around the rod 356 by a retainer nut Soll to prevent direct communication between the upper and lower pump cylinder sections.

The upper pump piston head S24) is slidingly sealed in an insert S62 by suitable piston rings S64 to provide a pumping action upon recprocation of the piston head 829, as will be described. The insert 862 is threaded at its upper end to the lower end of the middle plug @ld and is sealed at its lower end to the adapter 832 by a suitable sealing ring 866. Thus, the insert 862 forms an upper pumping chamber 868 between the lower face of the pump piston S20 and the upper end of the adapter 832.

A traveling valve S76 is positioned in a valve chamber S72 in the upper pump piston head S26). The traveling valve 879 is adapted to cooperate with an upwardly facing valve seat S74 secured in the lower end of the valve chamber 872 by an adapter 876 which is utilized to interconnect the piston head 320 with the hollow rod 856. It will also be noted that radial ports 878 are formed through the adapter i576 to provide communication between the pump chamber 36S and the valve chamber 872 and the upper end of the hollow rod 855. A valve stern 8d@ depends from the traveling valve 874D and is guided by a tubular guide S32 formed concentrically in the valve seat $74 to maintain the traveling valve concentric with the valve seat. Ports S84 extend from the uppper end of the valve chamber 872 upwardly and outwardly into communication with the upper end of the piston head 82d for the discharge of pumped well fluids therethrough, as will be hereinafter described. Also, a chamber S586 is formed in the upper end portion of the piston head di@ in a position to provide communication between the lower end of the hollow connecting rod 754 and the ports Stllor the discharge of exhausting power fluids into the upper end of the insert 862, as will also be hereinafter described.

The lower pump piston head 22 is provided with an auxiliary traveling valve S33 adapted to reciprocate in a valve chamber 89? extending from the central portion to the lower end of the respective piston head. The traveling valve 8% cooperates with an upwardly facing valve seat S92 which is retained in the valve chamber 89u by a retainer nut 894 to provide for an upward liow of l'luids through the valve chamber 89d but to prevent a downward ilow of fluids .through this valve chamber. The valve stem 8% of the valve 888 is guided by a tubular guide 898 formed concentrically in the valve seat 892 to retain the valve concentric with the seat. A port extends from the upper end of the valve chamber 894) to the upper face o the pump piston head 822 for the ilow of pumped well tluids therethrough, as will be described. Also, a port @02 extends through the piston head 822 from the lov/er end of the hollow rod 85d to the lower end. of the piston head 322. for the ow of well tluids from a lower pump chamber @iid between the lower piston head 822 and the standing valve 842, as will be described.

The overall operation of the pump unit 7% is best followed by reference to the schematic illustration of FIG. 13. High pressure power iiuid is constantly fed through the tubing 724 extending from the top of the well to the pump unit 700. This high pressure power duid ilows downwardly through the tube 73d which forms an inlet for the pump unit. Power fluid from the tube 730 Hows through the port 736 into the lower end of the upper engine cylinder section 7% as well as flowing downwardly through the hollow rod 7M and the port 748 in the lower engine piston head 7ll2 into the lower end of the lower enginercylinder section 7h25. Thus the high pressure power Huid is constantly acting on the lower face of each of the engine piston heads 7l@ and 7l2 to constantly urge the engine piston assembly in an upward direction. With the valve mechanism 752 in the position illustrated in FG. 13, the port 748 is closed with respect tothe passageway formed by the sleeve 76S and this latter passageway is placed in communication with the port 792 to provide the same pressure in the upper end of the lowerV engine cylinder section 7% and the hollow connecting rod 75d.v Since the hollow connecting rod 7 S4 is in constant communication with production column iluid pressure through the port 83d, the upper end of the insert S62 and the port S28, the upper end of the engine cylinder section 7198 will likewise be at production column pressure when the valve mechanism 752 is in the position shown in FIG. i3. t will also be noted that the upper end of the upper engine cylinder section 706 is in communication with the same pressure through the port 740 and the tube 742 communicating at its lower end with the upper end of the engine cylinder section 708. Therefore, the upper laces of the engine pistons '710 and 712 will be exposed to a lower pressure than the lower faces of these pistons to provide an upstroke for the pump unit 706. During such an upstroke, 'the iluid standing in the upper ends of the engine cylinder sections 7% and 79S will be exhausted downwardly through the various ports and passageways into the hollow connecting rod 754 and then will flow `back upwardly through the ports 88d, the upper end of the insert S62. and the ports 82S into the production iluid column.

At theV end of the upstroke the Valt/e mechanism 7:32 is shifted in the manner previously described and is disclosed in U.S. Patent No. 2,943,576; whereupon the port 748 is placed in communication with the passageway provided by the sleeve 763 and the port 792 is closed. The power uid in the lower end of the engine cylinder section 763 will then be directed through the valve mech-v anism 752 and the sleeve 763 into the upper end of the cylinder section 7% to act in a downward direction on lthe upper face of the engine piston head 7l2. rhis power iluidwill also ilow on upwardly through the tube 742 and the port 74@ into the upper end of the upper engine cylinder section 7% to act in a downward direction on Y the upper'face of the upper engine piston head 7M.V ln

an operative pump unit structure, the tube 73@ willV have a smaller diameter than the hollow connecting rod 754, such that the combined areas of the upper faces of the pistons 7l@ and 712 will be larger than the combined area of the lower faces of these pistons. As a result,

, when all of these areas are subjected to power iluid prest will be apparent that the pump piston assembly comprising the heads S2@ and $22 and the hollow rod S56 will be reciprocated simultaneously with the engine piston assembly by virtue of the connection of the hollow connectingrod 754 between these two assemblies. On the upstroke of the pump piston assembly, any iluid standing in the upper end of the lower pump cylinder section 318 will be forced upwardly through the ports 836 into the production column. It will be apparent that the auxiliary traveling valve 383 will be held in a closed position during this stroke by virtue of a downwardly acting pressure differential thereacross. It will also be apparent that any liuid standing in the upper end of the insert S62 will be forced, upwardly through the port 82S into the production iluid column since the traveling valve 37) will` also be closed by virtue of a downward acting pressure difierential. lt will also be recalled that during this stroke of the pump unit 7Gb, power fluid is exhausted from the engine end of the unit'through the hollow connecting rod 754i to join with well lluids in the upper end of the insert S52 tor discharge through the port 823.

Also on the upstrolie of the pump piston assembly, well fluids are drawn in through the inlet 848 around the standing valve 842 into the lower pump chamber 91M. It will further be apparent that a suction is created in the upper pump chamber 868 through the ports 878, rod 856 and port 9M, such that the upper pump chamberA 86h will be filled with well fluid simultaneously with the lower pump chamber 904. Both the main traveling valve 870 and the auxiliary traveling valve 33S are closed during such upstroke.

On the downstroke of the pump piston assembly, the standing valve 842 is closed and a portion of the well iluid standing in the lower pump chamber 9M is forced upwardly around the auxiliary traveling valve 888 and through the port 9th) into the upper end of the lower pump cylinder section 818. rlfhe remainder of the well fluids in the lower pump chamber 994 is forced upwardly through'the port 902 and hollow rod 856 to raise the main traveling valve 875i; whereupon these well fluids are directed on upwardly through the port 834 into the upper end of the insert 362. Simultaneously, well'uids standing in the upper pump chamber 368 are forced through the port S78 and around the main traveling valve d'7@ for joinder with the well fluids owing from the lower pump chamber 904. As a result, a rather small portion of the well iluid drawn into the pump unit on the upstroke will be discharged through the port 328 on Y the downstrolre of the pump unit, such that the pump end 7M- will be what is considered in the art a single acting pump. lt should be noted, however, that during the downstrolie of the pump piston assembly the upper face of each of the pump piston heads 82@ and 822 is exposed to production column pressure, such that a minimum force is required for moving the pump piston assemblyy on a downstroke.

ln reviewing the construction and operation of the pump unit 7Gb, itwill be observed that the engine piston assembly provides two sets of working faces facing in opposite directions, with each set bof working faces having a combined area larger than a cross section of the engine cylinder. Therefore, the horsepower output of the complex engine 792 will be substantially greater than the horsepowerfoutput of a simple engine. The complex pump end 7de provides two pumping chambers which are simultaneously iilled on theV upstroke of the pump unit and exhausted on the downstroke of the pump unit. ,k

action of production column pressure on Vthe upper faces of both of the Vpump pistons on the downstroke further minimizes the compression forces required to be exerted `through thehollow connecting rod 754. Thepump end 704 requires a single standing valve and yet obtains a pumping capacity commensurate with the capacity of a double acting pump. The auxiliary traveling valve S88 may be of appreciable size as illustrated in FIG. 12 to minimize the cost of the structure.

The pump unit illustrated in FIG. 14 and generally designated by reference character 1000 is provided as another illustration of a complex engine end and complex pump end having an increased capacity over the 'construction illustrated in the pump unit 700 of FIG. 13. The pump unit 1606 comprises a complex engine end 302 of the same construction illustrated in FIGS. through 7 and previously described in det-ail. This design of complex pump provides the maximum areas for the working faces of the engine piston assembly whe-rein only two engine piston heads are used to provide a maximum horsepower output.

The complex pump end of the unit 1090 is substantially the same construction illustrated in FiG. 13 and has been given the same reference number of 704. The only difference between the complex pump end as illustrated in FIGS. 13 and 14 is that the upper pump piston head 820v in lFIG. 14 is enlarged and slidingly cooperates with the upper pump cylinder section S16, rather than in an insert as shown in FIG. 13. Therefore, the complex pump end shown in FIG. 14 will have an increased capacity over that shown in FIG. 13. This design of complex pump end corresponds to the design of the complex engine end 302 to provide a complete pump unit having a maximum capacity and a maximum horsepower output which is particularly useful in relatively deep wells having substantial production. It will also be noted that the pump unit 1000 is a free-type pump unit as contrasted with the insert-type pump unit 700 illustrated in FIG. 13.

From the foregoing it will be apparent that the present invention provides a novel subsurface uid operated pump unit which will eiioiently and economically produce an oil well having substantially any production and horsepower requirements. The complex engine of this invention provides the maximum working areas on the engine piston assembly for the diametrical size limitations to provide an increased horsepower output with a minimum increase in pressure requirements for the power iluid used for operating the engine. As a result, the power iiuid can be maintained at a minimum pressure for a safe and economic well installation. The complex pump end of this invention provides a pump having a maximum capacity with a minimum of cost. It will further be apparent that the pump unit of this engine is simple in construction and will have a long service life.

Changes may be made in the combination or arrangement of parts or elements as heretofore set forth in this specification and shown in the ydrawings without departing from the spirit and scope of the invention as defined in the following claims.

I claim:

1. A subsurface well pump, comprising:

a pump cylinder of a size to be inserted in the well and having an upper end and a lower end,

said pump cylinder having a single well lluid inlet in the lower end thereof and having a lluid outlet therein spaced upwardly from the inlet,

a downwardly closing and upwardly opening standing valve assembly in Ithe inlet,

a pump piston assembly reciprocally disposed in the pump cylinder and providing a lower pump chamber between the lower end of the pump piston assembly and the standing valve assembly,

a connecting rod extending from the piston assembly to the upper end of the pump cylinder,

drive means 'connected to the connecting rod for reciprocating the pump piston assembly in the pump cylinder,

los,

25 said pump piston assembly comprising upper and lower piston heads and a hollow rod interconnecting said` piston heads, one of said piston heads being smaller than the other, and the large piston head being slidingly sealed in the pump cylinder,

said pump cylinder having a packer therein between the inlet and the outlet providing a sliding seal around the hollow rod, whereby an annular pump chamber is formed underneath the upper piston head, tubular insert secured con'ce-ntrically in said pump cylinder and extending iro-m said packer around said smaller piston head to one end of the pump cylinder, said insent being sealed to said packer and the respective end of the pump cylinder, and said smaller head being slidingly sealed in said insert to provide a reduced diameter pump chamber below the respective head,

the lower piston head having a bore therein providing communication between the lower pump chamber and the hollow rod,

the upper piston head having a port therein providing communication between the upper pump chamber and the hollow rod,

means forming a passageway through the upper piston head `from the hollow rod to the pump cylinder above the upper piston head, and

a downwardly closing traveling valve assembly in said passageway, whereby iluid is Idrawn into both pump chambers on the upstroke and forced therefrom through said passageway on the do-wnstroke.

2. A well pump as defined in claim 1 wherein the lower piston head has a bleed port therethrough communicating at one end with the lower pump chamber and at its other end with the pump cylinder above the lower piston head, and a downwardly opening check valve in said bleed port to prevent the ilow of well fluid through said bleed port from the lower pump chamber and yet provide a bleed :of fluid trapped between the lower head and said packer into the lower pump chamber.

3. A pump as defined in claim 1 wherein said insert extends from said packer to the upper end of the pump cylinder and has ports in the upper end thereof communieating with said outlet.

4. The pump as defined in claim 1 wherein said insert extends from said packer to the lower end of the pump cylinder and has an outer diameter less than the inner diameter of the pump cylinder to provide an annular passage from the lower end .of the pump cylinder around said insert to the level of the packer, and wherein ports are provided in the upper end of said insert and the lower end of the pump cylinder providing communication through said passage trom the well uid inlet below the standing valve assembly to the upper end of the lower piston head.

References Cited in the file of this patent UNITED STATES PATENTS 523,240 Rodenbaugh July 17, l1894 940,192 Rexroth Nov. 16, 1909 1,543,488 Todd June 213, 1925 2,156,537 Mathews May 2, 1939 2,166,612 Scott July 18, 1939 2,233,013 Humason et al Feb. 25, 1941 2,262,128 Zehner Nov. 1l, 1941 2,284,505 Zehner May 26, 1942 2,446,748 Etter Aug. 10, 1948 2,684,639 Sutton July 217, 1954 2,718,880 Deitrickson Sept. 27, 1955 2,917,000 English Dec. l5, 1959 2,943,576 English July 5, 1960 

1. A SUBSURFACE WELL PUMP, COMPRISING: A PUMP CYLINDER OF A SIZE TO BE INSERTED IN THE WELL AND HAVING AN UPPER END AND A LOWER END, SAID PUMP CYLINDER HAVING A SINGLE WELL FLUID INLET IN THE LOWER END THEREOF AND HAVING A FLUID OUTLET THEREIN SPACED UPWARDLY FROM THE INLET, A DOWNWARDLY CLOSING AND UPWARDLY OPENING STANDING VALVE ASSEMBLY IN THE INLET, A PUMP PISTON ASSEMBLY RECIPROCALLY DISPOSED IN THE PUMP CYLINDER AND PROVIDING A LOWER PUMP CHAMBER BETWEEN THE LOWER END OF THE PUMP PISTON ASSEMBLY AND THE STANDING VALVE ASSEMBLY, A CONNECTING ROD EXTENDING FROM THE PISTON ASSEMBLY TO THE UPPER END OF THE PUMP CYLINDER, DRIVE MEANS CONNECTED TO THE CONNECTING ROD FOR RECIPROCATING THE PUMP PISTON ASSEMBLY IN THE PUMP CYLINDER, SAID PUMP PISTON ASSEMBLY COMPRISING UPPER AND LOWER PISTON HEADS AND A HOLLOW ROD INTERCONNECTING SAID PISTON HEADS, ONE OF SAID PISTON HEADS BEING SMALLER THAN THE OTHER, AND THE LARGE PISTON HEAD BEING SLIDINGLY SEALED IN THE PUMP CYLINDER, SAID PUMP CYLINDER HAVING A PACKER THEREIN BETWEEN THE INLET AND THE OUTLET PROVIDING A SLIDING SEAL AROUND THE HOLLOW ROD, WHEREBY AN ANNULAR PUMP CHAMBER IS FORMED UNDERNEATH THE UPPER PISTON HEAD, A TUBULAR INSERT SECURED CONCENTRICALLY IN SAID PUMP CYLINDER AND EXTENDING FROM SAID PACKER AROUND SAID SMALLER PISTON HEAD TO ONE END OF THE PUMP CYLINDER, SAID INSERT BEING SEALED TO SAID PACKER AND THE RESPECTIVE END OF THE PUMP CYLINDER, AND SAID SMALLER HEAD BEING SLIDINGLY SEALED IN SAID INSERT TO PROVIDE A REDUCED DIAMETER PUMP CHAMBER BELOW THE RESPECTIVE HEAD, THE LOWER PISTON HEAD HAVING A BORE THEREIN PROVIDING COMMUNICATION BETWEEN THE LOWER PUMP CHAMBER AND THE HOLLOW ROD, THE UPPER PISTON HEAD HAVING A PORT THEREIN PROVIDING COMMUNICATION BETWEEN THE UPPER PUMP CHAMBER AND THE HOLLOW ROD, MEANS FORMING A PASSAGEWAY THROUGH THE UPPER PISTON HEAD FROM THE HOLLOW ROD TO THE PUMP CYLINDER ABOVE THE UPPER PISTON HEAD, AND A DOWNWARDLY CLOSING TRAVELING VALVE ASSEMBLY IN SAID PASSAGEWAY, WHEREBY FLUID IS DRAWN INTO BOTH PUMP CHAMBERS ON THE UPSTROKE AND FORCED THEREFROM THROUGH SAID PASSAGEWAY ON THE DOWNSTROKE. 